This invention relates to environmental control systems for supplying air to aircraft cabins.
A percentage (40%-50%) of cabin air is commonly recirculated in modern aircraft to conserve fuel consumption. Before "used" air can be reinjected into the cabin, it has to be filtered to remove contaminants and dehumidified to remove moisture. Also, "fresh" ambient air is mixed with the recirculated air to replenish the oxygen level and any lost volume.
To obtain cold fresh air, hot air is first bled from the gas turbine, off a compressor or fan stage. This hot air is then conditioned by running it through a "cool pack", such as Model No. EC300, manufactured by Hamilton Standard, a division of United Technologies Corporation.
The conditioned air, which is often below freezing, is then piped into a large plenum chamber, where it mixes with the warmer used air from the cabin. Because the used air is moisture-laden, it condenses upon being cooled in the mixing chamber. In addition, if there is a large-enough pressure drop in the plenum chamber, the fresh air (which is usually slightly pressurized) also gives up moisture. Unless this moisture is removed from the mixed airstreams, these particles would discharge into the cabin creating a foggy or misty atmosphere; or, on occasions, these particles could freeze into ice which would clog flow passages or be carried into the cabin. Therefore, water separators or dehumidifiers are typically added to prevent these conditions from happening.
Prior air mixers have drawbacks. For example, their inlet pipes with the freezing fresh air sometimes get blocked with ice upstream of the intended mixing; and, if mixing does occur in plenum chambers, the abrupt entwinement of different-temperature airstreams there is noisy. Also, their associated separators do not always remove sufficient moisture to prevent fogging.
Some effective separators tend to use stator vanes to impart a swirl to the moisture-laden fluid. This causes a centrifugal effect to throw entrained heavier particles (like water droplets or contaminants) against an interior wall, from where they are collected and removed.
However, they are typically used only with a single airstream (e.g., the recycled airstream), and are not used to mix or entwine two disparate airstreams, on opposite faces of the stator vanes, to create a thorough mixing through a cyclone effect that removes moisture from both streams. That would be a more effective dehumidifying system.
Accordingly, it is a principal object of the present invention to provide a unique air mixer and water collector, for supplying dehumidified air to aircraft cabins, that overcomes the aforementioned deficiencies of the prior art.
It is another general object to provide a highly efficient air mixer which is also capable of removing entrained moisture from the joined airstreams.
It is yet another general object to provide such a device which is smaller in diameter and generates less noise than present plenum-type mixers.
It is another object to provide an air mixer/water collector, commensurate with the above-listed objects, which has no moving parts and is extremely durable to use.